You could have knocked me over with a feather

You could have knocked me over with a feather.

Fig. I was extremely surprised.; I was so surprised that it was as if I was disoriented and could have been knocked over easily. When she told me she was going to get married, you could have knocked me over with a feather. John: Did you hear that they are going to tear down city hall and build a new one—price tag twelve million dollars? Sally: Yes, and when I heard that, you could have knocked me over with a feather.

See also: could, feather, have, knock